Safety control device for heating burners



Feb. 16, 1954 SAFETY CONTR J. BAscl' 2,669,298

OL DEVICE FOR HEATING BURNERS Filed Feb. 20, 1951 2 Sheet's-Sheet l INVENTOR. JOSEPH BASL'I Z4 .AGENT Feb. 16, 1954 J. BAscl SAFETY CONTROL DEVICE FOR HEATING BURNERS 2 Sheets-Sheet 2 Filed Feb. 20, 1951 Patented Feb. 16, 1954 SAFETY CONTROL DEVICE FOR HEATING BURNERS Joseph Basci, Brooklyn, N. Y.

Application February 20, 1951, Serial N 0.

1 Claim. (Cl. 158-28) This invention relates to new and useful improvements in burner control systems and more particularly to an improved electronic safety control system for fluid or gas burners.

In the operation of oil burners it is desirous to prevent an abnormal discharge of fuel into the burner in the event of ignition failure or the premature extinguishment of the flame; and in the operation of gas fired furnaces, ovens, etc., it

or short circuit in the control means therefor a power failure, or the excessive overheating of the burner walls, and, in some instances, to reactuate the igniting means in the event of flame failure.

One object of the invention is the provision of a highly eficient control system which is applicable to both gas and oil burners and which is effective to provide all of the desirous results listed above.

According to the invention there is provided a flame sensitive device which in the case of an oil burner may be a photo-tube and which in the case of a gas burner may be a flame rod, an electronic amplifier controlled by the flame sensitive device, control circuits operated by the amplifier, and a thermal switch actuated by a continued non-operation of said control circuits.

Another object of the invention i the provision of control circuitry for concomitantly reactuating the ignition means in the event of flame or ignition failure and for initiating an operation of the thermal switch, which, however, does not operate if the flame is reignited.

A controlling factor in the manufacture and marketing of control systems of the type involved is cost, both original and maintenance.

A further object of the invention, therefore, is to construct the device of the invention in such manner that the same is capable of being manu-.

factured economically, is capable of long life with a minimum of maintenance, and is adapted to rapid disassembly for adjustment and repairs.

Other objects and features of the invention will become apparent from the following description when read in the light of the accompanying drawings of which:

Fig. 1 is a perspective view of the control unit of the invention in condition for mounting.

Fig. 2 is an exploded perspectiv view of the several component parts of the unit.

Fig. 3 is a perspective view of the unit that illustrates the means for securing two of the casing components thereof together.

Fig. 4 is a sectional view on line l& of Fig. l with many non-essential details left out.

Fig. 5 is a detached side elevational View of the thermal switch of the invention, said switch being shown in mounted condition in Fig. 2.

Fig. 6 is a detached edge view of said switch.

Fig. '7 is a detached elevational view of the opposite side of the switch.

Fig. 8 is a fragmentary, of the switch, and,

Fig. 9 is the wiring diagram of the invention.

Referring first to the wiring diagram of Fig. 9, the circuit illustrated therein is primarily adapted to an oil burner but is readily adapted for use with a gas burner. As shown, the circuit includes an ordinary three wire thermostat 5, a high limit control unit it, the burner motor H, the burner ignition unit It, a transformer 23 having its primary coil 2| connected to A. C. supply and having a pair of secondary coils 22 and 23, a pair of relays RY! and RYE, a thermal switch 24, an electronic amplifier 25, preferably a dual triode such as a l2SN7, and a photo-tube 25 situated adjacent the burner flame and controlling said amplifier. For rotary pot type oil burners, the photo-tube 28 is replaced by a flame rod 27. For gas burners with pilot flame control, the flame rod 27 is used on the pilot name, the main gas valve replaces the motor 51, and the ignition circuits are eliminated.

The one side of motor i! and ignition unit It are connected by a lead 28 to one supply line 30. The other side of the motor, however, is connected by leads 3! and 32 through a normally opened contact 33 of relay RY! to the other supply line 34, and ignition unit it is connected with lead 34 by leads 35 and 36 through normally closed contacts 3? of relay RY2. Thus a normally open contact is provided in the motor circuit, and, said open contact along with a normally closed contact control operation of the ignition unit. Motor control relay RYI is connected by a lead 38 with one side of secondary coil 23 and by a lead 48 with a normally open contact t! of the thermostat l5. Closure of contact ll completes a circuit through a second contact 22 of the thermostat, lead 43, normally closed contacts M of relay RYZ, lead 45, thermal switch 2 1 and lead 46 to the other side of transformer coil 23.

The construction thus far described is such that operation of thermostat l5 energizes relay RYI which closes contacts 33 and initiates operation of ignition unit 18 and motor I1.

enlarged sectional View Relay RYI is also provided with normally open contacts 41 which are connected by an extension 48 of lead Mi with one side of coil 23 and by a lead 58 to the heater filament SI of amplifier 25. By means of a surge limiting resistor 52 and the lead 38, the other side of the heater filament is connected back to coil 23. Thus, on energization of relay RYI, a circuit is completed to heater i through contacts 41 and surge limiting resistor 52.

Completing a circuit to a heater filament, normally occasions a current surge equal to six or seven times the normal current drawn by the heater, which greatly reduces the'life of the tube. By inserting the resistor 52 in the circuit this current surge is limited to approximately twice the normal value which not only lengthens the life of the tube, but also lessens the standby power requirements and eliminates the need for a special heater winding on transformer 20. This arrangement, of course, is highly'advantageous in that it lowers both the initial and maintenance costsof the device.

Amplifier 25 maybe connected inany desired manner but preierablyis-connected as shown in Fig. 9. For convenience, the two halves of amplifier 25 will be referred to as tubes A and B, the left hand one in Fig. -9 being tube A. As shown the cathode 5-5 of tube A is connected to a tap of coil 22. The grid 58 of tube-Ais connected by alead 50 through a large resistor El to the anode B2 of photo-tube 26. A large resistor 63 and a capacitor 64 are connectedacross leads 56 and 60. Resistances E3 and 6! and condenser'64 must be properly proportioned to'provide proper bias for tube A and to provide a time constant of the proper value to maintain thebias during the negative swings of the coil 22.

Suggested values for these resistors and for the other circuit components will be listed at the end of the description. The anode 65 of tube A is directly coupled to the grid 58 of tubeB and through a large resistor 66 and lead 6'! to the other end of transformer coil 22. A smaller resistor 63 also connects said anode to the cathode of tube B. The anode of tube B is connected through .the coil of relay RYZ and a lead 69 to lead-'61 and transformer coil 22. By meansv ofa lead in and a capacitor ii, the .cathodeof tube 3 which is connected to the tap of coil 22, is coupled back to the anode 620i photo-tube 25.

The operation is-asfollowsz assumingthata flame is causing photo-tuber2fi to conduct, the latter rectifies the A. C. voltages-applied through lead 'lfi'from the, tap of coil 22. Thus,;a pulsating D. C. bias is applied to tubeyA causing the latter to become non-conductive. The charge on condenserfi l maintains the bias at a level sumcient for cutoff during the negative swings of coil 22. When tube A is out oif, the potential of its plate rises causing an increased current: flow. in tube B. Thisenergizes relay RY2. Inorderto maintain relay RY2 energized during the negative swings of coil 22, a large capacitor 12 isconnected across the coil thereof.

The construction of the amplifier issuch that when photo-tube 26 is conducting, or rectifying, the relay RYZ is energized, but when the phototube becomes non-rectifying. the cathode to grid connection of tube A is opened and the relay is deenergized.

It will be remembered that as described above, anoperation of thermostat I5 effects energization of motor starting relay RYLwhichthrough the contacts associated therewith closes the motor and ignition circuits through a thermal switch and also closes a circuit for the heater of amplifier 25. Normally, closure of the motor and ignition circuits effects lighting of the flame in the burner, which through photo-tube 26 and amplifier results in energization of relay RY2. This opens the normally closed contacts 31 and 44 of said relay which open the ignition unit circuit and the circuit for relay RYl' through thermal switch 2d respectively. However, normally open contacts E5 of relay RYZ are closed and complete circuit for relay RY! which does not include ther- *18, a common contact 88 5| of the latter, lead 40, relay mal switch 2%. This circuit includes the lead 45 which is also connected to contact as, a lead It,

closed contacts i? of energized relay RY! a lead of thermostat l5, contact RYl, lead 38, transformer coil 23, leads it and it, closed contacts ill of relay RY l, lead '58 and a lead 81 connected back to contacts 15.

The construction is such that immediately following a successful operationof ignition unit [.8- under control of thermostat I5, photo-tube 26 and amplifier 25 effect both the deenergizationof said ignition unit and also the shunting ofthe thermal switch 24 so that the latter does not heat up sufficiently to open the circuit and turn ofi motor IT.

Thermal switchZti preferably is of the-unique construction to bedescribedhereinafter but may be of any type capable of opening positively :in

approximately 50seconds due tothe heat .provided by approximately one watt of-power,.=and capable also of being reset manually within .a short period of time.

Thus, if'the ignition unit it fails to ignite a flame within the predetermined period of -approximately 50 seconds the thermal switch 24 opens and prevents the further pumping offuel into the burner by deenergizing relay RYI. Further, if the flame should be extinguished prematurely, the photo-tube. 26 becomes non-rectifying and relay RYZ is deenergized, bringing ignitionunit I8.and thermal switch2 i backinto the circuit. This of course, results either in :a successful operation of theuignition unit l8 .or in the opening of thermal switch 25. Tubefailures and short or open circuits in either relay RYZ or RY! also result in opening of thermal switch 24 since the shunt circuit for thermal switch 28 includes contacts 15 and. s1 iii-series with each other. Thus, accidental closure-of either contacts 25 0rd! is not sufficient to shortcircuitthermal switch 22, but rather both contacts .15 and 41 mustbe simultaneously closed to establish a bypass vorshort-circuit for thermal switch 24.

-It is believed evident that the opening of thermostat I5 conditions the device for the next oper-' ation.

It is desired that thermal switch 24 open in the event relay RY2 remains energized after thermostat I5 is opened, for example, when high infrared emission occurs due to overheated burner walls. This is accomplished by a circuit which includes said'switch, lead 36, transformer coil 23, resistor '52; heater 5!, leadsbc and 8!, closed contacts is of energized relay RY2 and lead 45.

The thermal switch of the invention is 'illus-' trated in detail in Figs. 5-8 and includes a plate 85 having. a shelf 86 bent off therefrom at one end and a shelf at the other end. A large opening in plate 85 extends into-shelf B'Iso that the latter resembles a pair of cars interconnected by-a crosspiece. Shelves 86 and 81- are Riveted to plate 85 between and spanning the portion of opening 88 adjacent shelf 81 is a plate 93 of an insulative material such as Bakelite. A tall 94 of plate 03 projects beyond shelf 81 and has secured thereto a pair of terminals 95 for the leads 46 and 45, 16 of the wiring diagram of Fig. 9. Secured in a hole in plate 93 and extending between the shelves 86 and 81 is a hollow stem 96 of brass or other conductive material, said stem having wound thereon a heating coil 91 which is insulated therefrom by a coating 88 of high temperature insulation. One end of the coil, however, is soldered to an annular flange or collar I the latter. The

stem 96 but fixed against rotation by a layer of solder I02 fixing it to the stem is a tubular pivot shaft I03 for a pinion I04. At the free end of stem 96 the end of shaft I03 is flared out at I and abuts a bearing washer I06 positioned between said flare and an annular collar I01 of said stem. A bearing washer I08 is also provided between pinion I 04 and the fixed end of stem 96.

It is to be mentioned that solder I02 may be of any commercially available type which will melt and free shaft I03 from stem 96 in approximately 50 seconds due to the heat generated by coil 91 with about one watt of power.

Cooperating with pinion I 04 is a pawl H0 of beryllium copper or the like which is connected by a lead III with the terminal 95 to which the heater coil is not connected. Pawl I I0 is secured to the flattened end of a rod II 2 of Bakelite or the like which is slidably mounted in holes in shelf 86 and in a shelf I I3 at the edge of opening 88. A pin II4 projects through rod H2 and into a slot I I5 in plate 85, that extends longitudinally of the rod and limits the amount of longitudinal movement thereof. Slot H5 also prevents rotative or chattering movements of rod II2. A spring H6 is wound on rod H2 and acts between shelf H3 and pin II4 to move the rod in a direction to rotate pinion I 04 counterclockwise in Fig. 7.

The construction is such that normally solder I02 is effective to prevent rotation of pinion I04 and a circuit is completed from one terminal 95 to the other through lead I 0| coil 81, stem 36, solder I02, shaft I03, pinion I04, pawl H0 and lead I I I. However, if solder I02 should be melted by coil 91, the pinion I04 is rotated by pawl IIO which moves out of contact therewith to the dotdash position of Fig. '1 and the switch is opened.

To reset the switch all that is required is to allow a few moments for the solder I02 to reharden, and to push rod I I2 back to its initial position, the pawl IIO readily springing to clear the upper portion of the pinion.

For convenience of installing and servicing the control device of the invention, the same is assembled in unitary form as shown in Figs. 1-4. The relays RYI and RY2, transformer 20, thermal switch 24 and amplifier 25 are mounted on one face of a rectangular boxlike chassis I I1 which includes two main plates H8 and I20 each having a side wall I 2| and an end wall I22 or I23 bent off therefrom. The side walls I2I and the end walls I22 and I 23 are, of course, oppositely located. Secured to plate I20 and to end wall I23 01' plate H8 are the pivot supports I24 of a hinge which also includes a removable pivot pin I25. Thus plates II 8 and I20 with their oppositely disposed Walls I2I and I22 or I23 form a box which is openable about hinge I24, I25 but which may be locked in closed condition by the engagement of a wide head screw 25 in an open end slot I21 in end wall I22. Screw I26 is threaded into a bracket I28 secured to plate II 8, and when drawn up, effectively prevents swinging movement of plate I20 about pivot pin I25.

The circuitry associated with relays RYI and RY2, transformer 20, thermal switch 24 and amplifier 25 is secured to the rear face of plate H0 and is covered and protected by an insulative plate I29 bolted to the bracket I28 and to another bracket I30. Secured to the forward face of plate I20 are a pair of insulative blocks I3I each having thereon a plurality of screw terminals to which the appropriate leads of a cable 32 extending from the circuit elements on plate H8,

openings I33 through which cables I34 are extended to connect the unit with a source of supply, a thermostat, a burner motor, etc.

Plate I20 is provided with suitable holes I35 by which the same may be mounted on a convenient wall or the like. The elements mounted on plate I I8 are covered and protected by a deep sheet metal cover I36 which embraces the plate H8 and slight portions of the side walls I2I and end Walls I22 and I23. Cover I36 is secured in place by a pair of screws I31 which are threaded into the end walls I22 and I23 and engage in open end slots I38 in the edge of the cover. In order to accommodate the reset rod II2 of thermal switch 24 a hole I40 is provided in cover I36.

It will be seen, therefore, that in the event thermal switch 24 operates as described above, the reset rod I I2 projects to the dot-dash line position of Fig. 1 through the cover hole I40, and can be reset merely by pushing it to the full line position illustrated. And, if it is desired to service the elements mounted exteriorly of chassis I I1, all that is required is to loosen screws I31 and remove cover I36. Further, to service the interior of chassis II1, the latter may be swung open on hinge I24, I25 by loosening screw I 26 or may be completely disassembled by removins pivot pin I25.

There has been provided, therefore, a highly efficient control unit for the purpose set forth that is not only economical in initial cost but also in installation and maintenance.

Suggested values for the several circuit constants are as follows:

Phototube 26 922 (vacuum). Transformer coil 22 225 volts, center tap 200 volts.

Transformer coil 23 24 volts.

While there has been described a preferred embodiment of the invention it is to be understood that many changes in details of the construc- Etion canabe =madeewithontlfden fiin f m vspiritzof the invention.

:and :a ;-normally deeenergized :electnicallyecontizolle'd. fuel feeding device,

and :compnisingza -:power :source, :a ffirst zrelay, cireuit means sior ienel gizingrsaidxfirst relayzby;said;:powerszso11ree in: response to 4: operation 30f :said :thermostat, a :controk'circuitzconnectedito asaictzfuel'z'feedinge'device, means for energizing said fuel feeding device ;insresponse ;to:energization ofl'asaidxzfirstrevlay, a themnal .switch including 21113916013163 heater-sin :saicl firstenamedccircuit :means-z operaltive :to qv'ideeenergize i said: relay :2 xpredetermined time. :after zener,gizationz.thereofizand zthenebylldisabling ElSaid. :control circuit,;;an -;electronicvampli- .fier. including aacontrol grid, =;a flame ssensitive means; for detecting the: presencearorzaabsence:Qf ax flame 1 in l the burner; -,cnnecte.d; in;- serieszwith ,said zcontrol -.gridf-to vary lthe pbiasz thereonrinaaG- :cordance ;-w-ith jthegpresenceizor absence wi the name, a -norma1ly,de-:energized= heater :filament for said amplifier, @means @for =-ene13gi2ing said ,sheater filament :u'pon energizationoi said first relay :to -renderv said amplifier- :tube .;.operative,-2:a

ifnrther re1ay,-.means for energizing 'said further relay 1 in response to ;operation of said amplifier in ,theipresence 0f sa flame, a normally-opened further control :1 circuit including. said means :for energizing said-heater. filament in shunt withsaid thermalxswitch, and. means for closing. said;.furether control circuit only response .to .simulltaneousuenergization.oLsaid first relay and said fnrthersrelay.

JOSEPH =BASC1I.

Referencesflited in the 1 file of this patent "UNITED-STATES PATENTS Number Name Date 17944332 'Wilmset a1. .Jan;.23,;1'934 12,051,368 Chapman Aug. 18,.1936 "2379,8571 -Beam et a1. July. 10, 1945 .,2,'.445,051' 'Wilson July 13, 19,48 .,2,490',09.5 Rosche Dec 6, 1949 2,493,412 Y'Lange Jan.. 3, 1950 2,539,208 Schulz et a1 Jan. 23, 1951 12556361 Feigal .June.,12, 1951 

